Width of the rectangle = x
Length of the rectangle = (x/3) - 3
Perimeter of the rectangle = 2 (Length + width)
= 2[(x/3) - 3 + x]
= 2[ (x - 9 + 3x)/3]
= 2[(4x - 9)/3]
= (8x - 18)/3
I hope the procedure is clear enough for you to understand and the answer has actually come to your desired help.